Traditional toilets require a user to directly contact the lids and seats of the toilets to open or close the toilet. This is neither convenient nor sanitary.
To solve the above mentioned problems, designers have developed automatic opening-closing devices which do not need the user to make direct contact with lids and seats of the toilet. A typical automatic opening-closing device for a toilet comprises a driving motor, a shaft capable of pivoting the seat or the lid of the toilet, and a speed reduction gear box connected between the motor and the shaft. However, in currently available automatic opening-closing devices, the reduction gear box is easily damaged when an excessive load is applied to the seat or lid. Moreover, because the existing opening-closing devices generally adopt a NGW planetary gear having a comparatively small gear ratio to reduce the speed of the output shaft, a speed reduction system with comparatively many stages is needed.